1 //===-- sanitizer_tls_get_addr.cc -----------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Handle the __tls_get_addr call.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "sanitizer_tls_get_addr.h"
15
16 #include "sanitizer_flags.h"
17 #include "sanitizer_platform_interceptors.h"
18
19 namespace __sanitizer {
20 #if SANITIZER_INTERCEPT_TLS_GET_ADDR
21
22 // The actual parameter that comes to __tls_get_addr
23 // is a pointer to a struct with two words in it:
24 struct TlsGetAddrParam {
25 uptr dso_id;
26 uptr offset;
27 };
28
29 // Glibc starting from 2.19 allocates tls using __signal_safe_memalign,
30 // which has such header.
31 struct Glibc_2_19_tls_header {
32 uptr size;
33 uptr start;
34 };
35
36 // This must be static TLS
37 __attribute__((tls_model("initial-exec")))
38 static __thread DTLS dtls;
39
40 // Make sure we properly destroy the DTLS objects:
41 // this counter should never get too large.
42 static atomic_uintptr_t number_of_live_dtls;
43
44 static const uptr kDestroyedThread = -1;
45
DTLS_Deallocate(DTLS::DTV * dtv,uptr size)46 static inline void DTLS_Deallocate(DTLS::DTV *dtv, uptr size) {
47 if (!size) return;
48 VPrintf(2, "__tls_get_addr: DTLS_Deallocate %p %zd\n", dtv, size);
49 UnmapOrDie(dtv, size * sizeof(DTLS::DTV));
50 atomic_fetch_sub(&number_of_live_dtls, 1, memory_order_relaxed);
51 }
52
DTLS_Resize(uptr new_size)53 static inline void DTLS_Resize(uptr new_size) {
54 if (dtls.dtv_size >= new_size) return;
55 new_size = RoundUpToPowerOfTwo(new_size);
56 new_size = Max(new_size, 4096UL / sizeof(DTLS::DTV));
57 DTLS::DTV *new_dtv =
58 (DTLS::DTV *)MmapOrDie(new_size * sizeof(DTLS::DTV), "DTLS_Resize");
59 uptr num_live_dtls =
60 atomic_fetch_add(&number_of_live_dtls, 1, memory_order_relaxed);
61 VPrintf(2, "__tls_get_addr: DTLS_Resize %p %zd\n", &dtls, num_live_dtls);
62 CHECK_LT(num_live_dtls, 1 << 20);
63 uptr old_dtv_size = dtls.dtv_size;
64 DTLS::DTV *old_dtv = dtls.dtv;
65 if (old_dtv_size)
66 internal_memcpy(new_dtv, dtls.dtv, dtls.dtv_size * sizeof(DTLS::DTV));
67 dtls.dtv = new_dtv;
68 dtls.dtv_size = new_size;
69 if (old_dtv_size)
70 DTLS_Deallocate(old_dtv, old_dtv_size);
71 }
72
DTLS_Destroy()73 void DTLS_Destroy() {
74 if (!common_flags()->intercept_tls_get_addr) return;
75 VPrintf(2, "__tls_get_addr: DTLS_Destroy %p %zd\n", &dtls, dtls.dtv_size);
76 uptr s = dtls.dtv_size;
77 dtls.dtv_size = kDestroyedThread; // Do this before unmap for AS-safety.
78 DTLS_Deallocate(dtls.dtv, s);
79 }
80
81 #if defined(__powerpc64__) || defined(__mips__)
82 // This is glibc's TLS_DTV_OFFSET:
83 // "Dynamic thread vector pointers point 0x8000 past the start of each
84 // TLS block."
85 static const uptr kDtvOffset = 0x8000;
86 #else
87 static const uptr kDtvOffset = 0;
88 #endif
89
DTLS_on_tls_get_addr(void * arg_void,void * res,uptr static_tls_begin,uptr static_tls_end)90 DTLS::DTV *DTLS_on_tls_get_addr(void *arg_void, void *res,
91 uptr static_tls_begin, uptr static_tls_end) {
92 if (!common_flags()->intercept_tls_get_addr) return 0;
93 TlsGetAddrParam *arg = reinterpret_cast<TlsGetAddrParam *>(arg_void);
94 uptr dso_id = arg->dso_id;
95 if (dtls.dtv_size == kDestroyedThread) return 0;
96 DTLS_Resize(dso_id + 1);
97 if (dtls.dtv[dso_id].beg) return 0;
98 uptr tls_size = 0;
99 uptr tls_beg = reinterpret_cast<uptr>(res) - arg->offset - kDtvOffset;
100 VPrintf(2, "__tls_get_addr: %p {%p,%p} => %p; tls_beg: %p; sp: %p "
101 "num_live_dtls %zd\n",
102 arg, arg->dso_id, arg->offset, res, tls_beg, &tls_beg,
103 atomic_load(&number_of_live_dtls, memory_order_relaxed));
104 if (dtls.last_memalign_ptr == tls_beg) {
105 tls_size = dtls.last_memalign_size;
106 VPrintf(2, "__tls_get_addr: glibc <=2.18 suspected; tls={%p,%p}\n",
107 tls_beg, tls_size);
108 } else if (tls_beg >= static_tls_begin && tls_beg < static_tls_end) {
109 // This is the static TLS block which was initialized / unpoisoned at thread
110 // creation.
111 VPrintf(2, "__tls_get_addr: static tls: %p\n", tls_beg);
112 tls_size = 0;
113 } else if ((tls_beg % 4096) == sizeof(Glibc_2_19_tls_header)) {
114 // We may want to check gnu_get_libc_version().
115 Glibc_2_19_tls_header *header = (Glibc_2_19_tls_header *)tls_beg - 1;
116 tls_size = header->size;
117 tls_beg = header->start;
118 VPrintf(2, "__tls_get_addr: glibc >=2.19 suspected; tls={%p %p}\n",
119 tls_beg, tls_size);
120 } else {
121 VPrintf(2, "__tls_get_addr: Can't guess glibc version\n");
122 // This may happen inside the DTOR of main thread, so just ignore it.
123 tls_size = 0;
124 }
125 dtls.dtv[dso_id].beg = tls_beg;
126 dtls.dtv[dso_id].size = tls_size;
127 return dtls.dtv + dso_id;
128 }
129
DTLS_on_libc_memalign(void * ptr,uptr size)130 void DTLS_on_libc_memalign(void *ptr, uptr size) {
131 if (!common_flags()->intercept_tls_get_addr) return;
132 VPrintf(2, "DTLS_on_libc_memalign: %p %p\n", ptr, size);
133 dtls.last_memalign_ptr = reinterpret_cast<uptr>(ptr);
134 dtls.last_memalign_size = size;
135 }
136
DTLS_Get()137 DTLS *DTLS_Get() { return &dtls; }
138
139 #else
140 void DTLS_on_libc_memalign(void *ptr, uptr size) {}
141 DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res) { return 0; }
142 DTLS *DTLS_Get() { return 0; }
143 void DTLS_Destroy() {}
144 #endif // SANITIZER_INTERCEPT_TLS_GET_ADDR
145
146 } // namespace __sanitizer
147